Known sleds, such as that disclosed in Sellers, U.S. Pat. No. 4,666,171, feature a strap extending transversely across the rider's knees. Such straps prevent the rider from pitching out of the sled. However, they do little to prevent lateral shifting of the rider's legs. Such lateral shifting is particularly pronounced during tight turns at high speed.
The involuntary lateral shift of the rider's legs during a turn can skew the sled's weight distribution. This can lead to loss of control, which at high speed, can be dangerous.